The invention relates to a device for printing flat workpieces.
Such devices generally include an application roller which rolls on the workpiece surface to be printed, and accordingly prints a printed image on the workpiece surface directly or indirectly, according to whether the application roller itself is constructed as a printing cylinder, or cooperates as a transfer roller with such, and applies a printed image to the workpiece surface, and also a counter-roller which, in cooperation with the application roller, forms a printing gap through which the workpiece passes during printing. Furthermore, a transport device is present for feeding the workpiece into and out of the printing gap formed by the application roller and the counter-roller.
In particular, to give derived wood product panels the appearance of real wood, on cost grounds as against real wood veneer or foil coatings, printed images of decorations and wood veining are directly applied to the derived wood product panels.
For the highest quality improved appearance, a single color printing is of course not suitable. Rather, it is desired to apply the veining or decoration to the material panel in multicolor printing. This is not only the case for derived wood products; uses for other materials which can be qualitatively improved by surface printing, such as for example brick or artificial leather, can be upgraded by multicolor printing.
However, specifically for a high-value multicolor printing, it is indispensable that the printed image is positioned on the workpiece within very close tolerances, typically in the region of ±0.1 mm. Only thus can an optical quality comparable with conventional foil coatings be attained.
These requirements are of course more difficult to maintain with the present flat workpieces than in machines for paper or foils, because the flat workpieces here do not run endlessly through the printing machine, and printing according to the pattern of paper sheet printing machines is in all cases not possible, because of the inflexibility of the flat workpieces concerned.